FIG. 12 is a side view showing a rubber track and a traveling device, and FIG. 13 is a side view showing the area around a driving wheel of the traveling device.
As shown in FIG. 12A, a conventional rubber track C comprises a rubber track body h formed from a rubber elastic body in an endless belt shape, a tensile reinforcing layer s2 and metallic cores m. The tensile reinforcing layer s2 is formed so that steel cords s1 are embedded in rows parallel to a circumferential direction in the rubber track body h. Each steel cord s1 is twisted from a plurality of steel wires acting as tensile reinforcements. The metallic cores m are embedded in the inside circumference of the tensile reinforcing layer s2 at a fixed interval in a rubber track circumferential direction as a reinforcement in the lateral direction.
A metallic core m comprises an engagement section m1 in the center region in the longitudinal direction of the core, guide projections m2 for preventing a wheel from coming off the track on both sides in the longitudinal direction of the core of the engagement section m1, and wing sections m3.
Further, there is also a core with a horizontally protruding body to prevent the track C from coming off the track traveling device (for example, see patent literature No. 1 that is identified hereinafter).
Generally, the rubber track C is used by being suspended on a coupled driving wheel (idler) A and a driving wheel (sprocket) S of an endless track traveling device M of, for example, a construction machine, etc., as shown in FIG. 12B. In the figure, T is a track frame, R1 is a lower rotary wheel, and R2 is an upper rotary wheel.
The rubber track C has a problem that the steel cords s1 of the tensile reinforcing layer s2 can be cut.
The steel cords s1 can be cut by various causes. As one of the causes, as shown in FIG. 13, the bottoms of the sprocket S clog with sand J so that the cores m rise from the bottoms between teeth of the sprocket, and an abnormal tensile force is imposed on the rubber track C.
Further, as another factor, cuts are caused by what water sinking in from cracks occurring on the rubber track, the steel cords s1 corroding, and a tensile force being imposed on the corroded portion.
To resolve the problem of the cutting of the steel cords, it has been suggested that the tensile force in the circumferential direction acting on a rubber track be equally dispersed on the whole steel cords (for example, see patent literature No. 2) and that an engagement section be provided to prevent the interval between the cores m adjoining one another in the circumferential direction in the rubber track body h from changing (for example, see patent literature No. 3).
Many rubber tracks having no steel cords (steel cordless rubber tracks) s1 have been suggested. For example, there are a connecting link type rubber track using a track link of a conventional metallic track (for example, see patent literature No. 4) and a rubber track carrying out a tensile reinforcement through members other than steel cords s1 (for example, see patent literature No. 3 or patent literature No. 5).
[Parent literature No. 1] Japanese utility model publication No. 04-067585 (especially, FIG. 6)
[Patent literature No. 2] Japanese patent publication No. 2007-022328
[Patent literature No. 3] Japanese patent publication No. 08-301154
[Patent literature No. 4] Japanese patent No. 3163481
[Patent literature No. 5] Japanese patent publication No. 2000-313371